core: print correct quit message when quitting, simplify code

"End of file" was printed to the terminal instead of "Quit" when exiting
with the "quit" slave command (closing the window and such). Note that
it will still print EOF when it exists because the end of the playlist
is reached.

Do some other (not strictly related) simplifications.
vo_caca: remove OSD support

Recent changes to the OSD code made vo_caca crash when showing OSD.
Since this is a joke VO (== I'd rather not waste my time with it),
remove the OSD support. It wasn't that great anyway.
demux_mf: map to codecs directly

Instead of going through FourCCs and codec_tags.c.
demux_rawvideo: allow setting video codec

Can be used to decode some obscure image formats and similar stuff.
demux_mf: support .xbm

And support the PIX_FMT_MONOWHITE pixel format. (This is really weird:
unlike PIX_FMT_MONOBLACK, it uses white pixels. I have no idea why
libavcodec doesn't just convert the pixel format on the fly, instead of
bothering everyone with really special pixel formats.)
Remove --rootwin option and rootwin property

You can just use --wid=0 if you really want this.

This only worked/works for X11, and even then it might interact badly
with most desktop environments. All the option did was setting --wid to
0, and the property did nothing.